Filament spring



Oct. 19, 1937. R, SMITH 2,096,205

FILAMENT SPRING Filed June 27, 1936 Li INVENTOR NEWELL R. SMITH ATTORNEY Patented Oct. 19, 1937 UNITED STATES FILAMEN T SPRING Newell R. Smith, Bloomfield, N. J., assignor; by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application June 2'7, 1936, Serial No. 87,603

4 Claims.

This invention relates to electron discharge devices, particularly to filament tensioning means for said devices.

It is desirable that filamentary cathodes be supported so that the filaments are always centered in the electrode assembly, and are kept taut to minimize vibration of the filament. Because of the linear expansion and contraction of the usual filament during heating and cooling, spring tensioning means at one end of the filament. are commonly used. The usual spring tensioning means for inverted V-type filaments comprises a resilient arm with a hook at one end to engage the bight or vertex at the upper end of the filament and are attached at its other end, laterally of the plane of the filament, to the upper insulating spacer of the electrode assembly. With such a filament support the hook and the bight of a filament moves in an arc about the outer end of the arm, as a center and displaces the filament with respect to the other electrodes. Constructions employing guides in which a filament hook reciprocates in a straight line have been proposed, but are expensive and are diflicult to assemble.

It is an object of my invention to provide a resilient spring support for filamentary cathodes which guides the upper end of the filamentary cathode in a straight line parallel to the axis of the electrodes, and which is easy and inexpensive to manufacture and assemble.

The novel features which I believe to be characteristic of my invention are set forth with particularlty in the appended claims, but the invention itself will be best understood by reference to the following specification taken in connection with the accompanying drawing in which:

Figure 1 is a view in perspective and partly broken away of an electron discharge device embodying my invention;

Figure 2 is a detailed perspective View of a filament support constructed in accordance with my invention.

The electron discharge device shown in Figure 1 has a metal envelope I closed at its lower end by a header 2 upon which is supported an electrode assembly 3 of the unit mount construction. The electrode assembly comprises an anode 4 and filament 5 positioned between transverse insulating spacing members 6 and l. A filamentary cathode 5 is shown by way of example as an inverted V with the lower end of its legs attached to the lower spacer 6.

In accordance with my invention the bight or vertex of the filament is passed over the center of .55 a novel filament tensioning means I0, comprising a short length of resilient spring metal either in the form of a wire or a fiat ribbon formed with two curved legs or loops II and I2, best shown in Figure 2, joined by a transverse section l3, over V which lies the bight of the filament. The outer 5 ends of the leg portions are provided with hooks I4 and i5, which may, upona slight compression of the spring, be inserted in openings provided in the insulating spacer 1.

It has been found convenient to snap myfila- 10 ment tensioning spring into place by engaging its end hooks in the insulating spacer, to thread the legs of the V-type filament through the openings of the spacer shown at I6 and lower the filament until its bight rests upon spring portion 15 I3, to depress the center section I3 a predetermined distance below the spacer, and to then secure the lower ends of the filament. By so assembling the spring and filament, an accurately predetermined tension may be placed upon the 20 filament spring so that in the course of manufacture all filaments of a group of tubes are tautened to the same degree.

During heating and stretching of the filament the bight of the filament supported by my im- 25 proved spring means moves vertically in a straight line, inasmuch as the compression of the two legs of the spring tensioning means is always equal and opposite for any depression of the center portion of the spring. 30

The filament spring may, if desired, be made of fiat or ribbon-like spring metal so that its end hooks l4 and I5 bear throughout their width upon the face of the insulating spacer and thus stabilize the filament spring on the fiat insulator. 35 Since the center portion [3 of the spring which carries the load of the filament passes through the insulating spacer and to a point ,beloW the outer ends of the spring, the tension placed upon the spring by the filament positively holds the spring 4 in an upright position as shown. The downwardly extending portions of the center section 8 3 may conveniently be guided in notches or slots H in the insulating spacer as shown.

In Figure 3 is shown a filament tensioning 4 spring embodying the characteristic features of my invention in which the legs of the spring member are relatively fiat and straight as compared to the curved'legs of the filament spring of Figure l. The straight portions of the legs 50 of the spring are joined to the lower transverse section l3 by curved portions l8, formed on the arc of a circle with the pivotal points at the hooks I4 and I5 as the centers of curvature. When section l3 moves vertically because of expansion or contractiongof the'ifilament'; curved portions I 8 slide throughi notches l1 without binding or'dise v V engaging. d v Good results have been obtained with filament: springs made 7 mils in diameter, about 30 centimeters long and of nonsag tungsten wire: about '7 tormed into the shape shown'in any standa rd punch presswithsmtable dies? Since many modifications may thereof, it is desired that the appended claims be l 'limited only by the prior art.;

20 r 7 7 portions; with fixedly secured at the lower I claim: 1. electron construction in said envelope with al filament resilient tensioning means ing' spacer ,and'a spring member sidelo fi' said ins "latin'g spacergsaid two portions heing joinedzlby a central section extending below said spacer andattacheditosaid other end of the filament.

'2'. In combinati'on, a.filament,"resilient tensioning means for said'fil'ament'comprising a spring with its cen'ter section attached to the filament,- the'spring havingcurvedlportions rising: in out} be'inade in my invention without departing from the scope} v discharge device comprising an: envelope, an electrode assembly of the unit mount end ofthe assembly for fsupporting the other end of the filament comprising aniinsuiat V V withtwoj leg 1 their. outer en'ds attached to one' wardly: extending conjugate curved loops, the

router ends'oi t e curved portions having hook V fastening means to engage a support, the fastenthe center section being in a com ingrneans and mon plane. 7

3. An' eIectro'ndischarge device nan insulating "spacer in said device, resilient filament tension ing means comprising'afspringettached at each V V the: springebeinggcurved in- 3 7 1 V M It: the loo'psbeing oined by an integral section end: to said 'spa'cer; V V wardly ,from its ends in two loops; the inner'ends below said spacer.

' 4. Resilientffilament tensioning" means comprising a" metal spring,1a flat sheetv of V insulation. fwith a'n opening, the ends of said spring-bein atltached to one's'ide of said spacer and having relaextending inwardly-to V ward each otherflfr'om s'aid ends,;the spring hav- 7 ing a center section on the; other side of said 7 V 1 r '20 by curvedta-portions ,of: thespring extending tively straight portio s spacer integrally joined to's aid straight portions through said opening," said curvedrportidns beinzl through ing. I H a NEWELLRQSMITH forfri'edion arcs with'said'ends as'centerssothat' V movement of said center sectionlaterally of saida spacer causes said curved portions to"v travel 2; the openingin saidspacer without bind- 

